INTRODUCTION TO PHARMACY -01

INTRODUCTION TO PHARMACY -01

What is a drug ?

Drug is a substance that acts on the central nervous system or kills disease-causing infectious organisms or affects the activity of a specific bodily organ or a narcotic (dulls senses and reduces pain).

The term ‘drug’ refers to any particle, whether natural or synthetic having therapeutic and medicinal properties and used in the diagnosis, cure, mitigation, treatment or prevention of diseases in man and other animals.

A drug is any chemical substances which changes a physiological function and modifies a disease process.

According to WHO definition, any substance or product that is used or intended to be used to modify or explore physiological system or pathological states for the benefit of the recipient is called drug.

The benefit of the recipients includes:
1. The diagnosis of disease (i.e. contrast media, e.g. barium salt, lopamidol are used for diagnosis for disease)
2. The prevention of disease (e.g. vaccine)
3. The control of disease (e.g. insulin)
4. The treatment of disease (antibiotics are used for treat infections)


Biological drug:
Those drug obtained from living sources are termed as biological drug.
Example:
Heparin: beef lung, porcine intestine
Insulin: human
Histamine: mast cell
Vaccine: human, microorganisms
Antibiotic: microorganisms
Anti-sera: horse serum

Prodrug:
Drugs that rely on metabolic conversion within the body into their active form are termed as prodrug.
Or, those drugs do not produce any pharmacological effect until they are chemically altered within the body are called prodrug.

Example:
Prodrug- Prontosil Talampicillin Diazepam
Active form- Sulfonamide Ampicillin Oxazepam

Properties of an ideal drug:
1. A drug molecule must have appropriate size, electrical charge, shape and atomic composition.
2. A useful drug must have the necessary properties to be transported from its sites of administration to its site of action.
3. A practical drug should be inactivated or excreted from the body at a reasonable rate so that its actions will be of appropriate duration.

Differences between drug and medicine:
Drugs are any substance which acts on the living body to alter the physiological process and are used for the prevention, diagnosis and treatment of disease. Dose not have a suitable form and dose.
Example:
For prevention: Vaccine
For diagnosis: Barium sulphate for peptic ulcer
For treatment: Antibiotic for infection


Medicine is any drug which has a definite form and dose and are therapeutically used for the treatment of disease of living subjects. Has a suitable form and dose.

Example:
Digitalis for the treatment of CCF
INH for the treatment of TB
Ranitidine for the treatment of peptic ulcer

OFFICIAL DRUG:
Any substance or drug (crude or prepared), which is included in the current issue of the pharmacopoeia of a country and is officially used for therapeutic purposes, is called an official drug.

UNOFFICIAL DRUG:
A drug, which has once been recognized as a drug in the pharmacopoeia, but not included in the current issue of the pharmacopoeia or any official drug literature, is designated as an unofficial drug.

NON-OFFICIAL DRUG:
A non-official drug is a substance, which possesses some medicinal properties and is unofficially used for therapeutic purposes, but has never been included as a therapeutic item in the pharmacopoeia or any official drug literature of any country.

Sources of drug:

1. Natural source:
Animal: Insulin, Heparin
Plant: Digitalis, Morphine
Microorganism: Penicillin, Chloramphenicol
Minerals: MgSO4.7H2O, Ferrous fumerate

2. Synthetic source (laboratory):
Aspirin, Paracetamol

3. Semi-synthetic source:
Ampicillin, Tetracycline

4. Biotechnological source:
Human insulin, Hepatitis B vaccine.

Classification of drugs:
1. According to Affinity and Efficacy

(tendency of drug to bind with receptor is termed as affinity; ability, once bound to receptor, to initiate changes, which lead to effects, is called efficacy).
Pilocarpine (muscarinic agonist), Atropine (muscarinic antagonist)

2. According to Therapeutic use:
Antimicrobial: Penicillins
Analgesics and Anti-Pyretic: Paracetamol, Aspirin

3. According to Mode or Site of Action:
(a)Molecular interaction: receptor blocker- propranonol
(b)Cellular site: loop diuretics- frusemide
(c)Physiological system: anti-coagulants- heparin

4. According to Molecular Structure:
Barbiturates: Phenobarbitone
Glycosides: Digoxin
Alkaloids: Quinine
Steroids: Dexamethasone

Routes of Drug Administration:

1. Systemic: whatever the route it is introduced drug ultimately goes to blood and then to the site of action.
(a) Entral or Alimentary rotes: sub-lingual, oral, rectal.
(b) Parenteral routes:

Injection:
Subcutaneous (S. C.)
Intracutaneous (I. C.)
Intravenous (I. V.)
Intra-arterial (I. A.)
Intramuscular (I. M.)
Intrathecal (I. T.)
Intra-articular (I. art)
Intraperitoneal (I. P)
Intraventricular
Intracardiac
Intrapleural
Intramedullary
Intralesional

Inhalation
2. Local: Applied to localized area and action is confined to that area.

(a)Topical application: (ointment, paste, drops, powder, lotion etc.)
Skin (rubbing of drug on the skin).
Mucous membrane of nose, urethra, rectum, anal canal, vagina.
Eye and Ear.

(b)Iontophoresis: drugs are applied to the skin and galvanic current is used to increase absorption through skin.

Basic Introduction of Different Types of Dosage Form

The form in which drug substances are presented in the market are called the dosage forms. A dosage form may be solid, semisolid or liquid (e.g. tablets and capsules; ointments and creams; solutions and suspensions etc.) and contains a definite quantity of drug (s).

The desirable properties of a dosage form are summarized below :

1. It should be convenient to handle, use and store. For better patient compliance, it should not disturb his routine life style as for as possible and should be acceptable aesthetically, organoleptically, therapeutically and from economic standpoint.

2. It should be stable during storage (shelf-life) and use. During storage the physical, chemical and therapeutic integrity of the dosage form should be maintained by assuring freedom from interaction between components with packaging materials and environmental factors (heat, humidity, oxygen, light). It should also withstand mechanical shock during transportation. The dosage form must retain its shape, size appearance, taste, flavor and therapeutic effect during the stipulated shelf-life.

3. The dosage form should be presented in different drug strengths providing flexibility of dose to suit different age groups or for different disease condition.

4. It should provide the anticipated therapeutic effect. The extent and pattern of drug release from the dosage form, onset, intensity and duration of action should be predictable.

5. It should protect the drug substance and conceal the disagreeable taste or odor.

6. It should be economical and presentation should be elegant.

7. Finally, it should permit easy identification through distinct color, shape or identification marking (s).


Classification of Dosage Forms:

1. According to Physical State: Solid, Semisolid, Liquid, Gaseous.

2. According to Route of Administration: Oral, Parenteral, Rectal, Nasal.

3. According to Site of Application: Skin, Eye, Ear, Tooth, Nose, Hair, Hand, Foot, Mucosal membrane.

4. According to Uses: Internal and External.


Aromatic Water
Aromatic waters are also known as medicated waters. They are dilute, usually saturated, aqueous solutions of volatile oils or volatile substances. Some of them have a mild therapeutic action but mainly they are used as flavoring agents in preparations meant for internal administration of drugs. Aromatic waters may be prepared either by diluting the concentrated waters or by shaking the volatile substances with water. Aromatic waters include anise water, camphor water, chloroform water, cinnamon water and peppermint water.

Cachets
Cachets consist of a dry powder enclosed in a shell, usually prepared from a mixture of rice flour and water by molding into a suitable shape and drying. They are quite useful for administering the drugs with unpleasant taste and a large dose can be enclosed in a cachet than in a tablet or capsule. There are two kinds of cachets; ‘wet seal' cachets which are sealed by moistening the edges with water, and `dry seal' cachets. Cachets should be stored and supplied in well closed air tight containers.

Ear Drops
Ear drops are the liquid preparations in which the drug or drugs are dissolved of suspended in a suitable vehicle like water, dilute alcohol, glycerin -or propylene glycol and are intended for instillation into the ear with a dropper. They are generally used for cleansing the ear, drying weeping surfaces, softening the wax and for treating the mad infections. Ear drops are dispensed in colored, fluted bottles attached with a dropper or in suitable plastic containers. The containers should be labeled "for external use only".

Elixirs
Elixirs are clear, pleasantly flavored, sweetened hydro-alcoholic liquid preparations for oral administration. The main ingredients of elixirs are ethanol and water but glycerin, sorbitol, propylene glycol; flavoring agents, sugar and preservatives may be incorporated to the preparation. The elixirs may be medicated or non-medicated. The medicated elixirs usually contain very potent drugs such as antibiotics, antihistaminic and sedatives. The non-medicated elixirs are used as flavors and vehicles.


Emulsions
Emulsions are the biphasic liquid dosage form of medicament in which two immiscible liquids (generally one of which is water and the other is some lipid or oil) are made miscible by the addition of a third substance as emulsifying agent. Emulsions are of two types (a) oil in water type (O/W) (b) water in oil type (W/O). The former is generally for oral administration whereas the latter is generally for application to the skin. Emulsions should be supplied in wide mouthed containers labeled with "shake the bottle before use" label.

Eye Drops
Eye drops are sterile aqueous or oily solutions or suspensions for instillation into the eye. They are usually applied into the space between the eye ball and eyelids or on to the corneal surface. The main requirement of eye drops is that they should be sterile, usually isotonic, buffered and free from foreign particles to avoid irritation to the eye. They usually contain substances having antiseptic, anesthetic, anti-inflammatory, mydriatic or miotic properties or substances used for diagnostic purposes. Eye drops should be dispensed in glass or suitable plastic containers with a screw cap fitted with a rubber teat and glass dropper for easy application of the drops or the containers may be fitted with a narrow nozzle from which the drops can be directly instilled into the eye.

Gargles
Gargles are aqueous solutions used for the prevention or treatment of throat infections. Usually they are concentrated solutions and should be diluted with warm water before use. Gargles should be dispensed in white fluted bottles.

Gels
Generally gels are the aqueous colloidal suspensions of the hydrated forms of insoluble inorganic drugs.

Inhalations
Inhalations are the liquid preparations containing volatile ingredients. They are used to relieve nasal congestion and inflammation of the respiratory tract. They may be placed on a pad or added to hot water and vapors inhaled for five to ten minutes.

Injections
Injections are the sterile liquid preparations containing one or more medicaments dissolved or suspended in a suitable vehicle and are meant for introduction into the body tissues by means of an injection under or through one or more layers of the skin or mucous membrane.

Lotions
Lotions are liquid suspensions or dispersions meant for external application to the skin without friction. They usually contain alcohol and glycerin because alcohol hastens drying and produces cooling sensation whereas glycerin keeps the skin moist for a sufficient long time. Lotions should be dispensed in a colored fluted bottle with "for external use only" and "shake the bottle before use" label.

Lozenges
Lozenges are the solid dosage form of medicament which is meant for slow dissolution in the mouth. Along with medicament-they contain a sweetening agent, flavoring agent and a strong binding agent. They may be prepared either by molding or by compression.

Mouthwashes
Mouthwashes are usually aqueous solutions in concentrated form with a pleasant taste and flavor used for rinsing, deodorant, refreshing or antiseptic action. Medicated mouthwashes may contain astringents, antibacterial agents, protein precipitants or other agents. They are generally used after dilution with warm water, on the mucous membrane of the mouth.

Nasal drops
Nasal drops are usually aqueous solutions intended for instillation into the nostrils by means of a dropper. They are commonly used for their antiseptic, local analgesic or vasoconstrictor properties.

Ointments
Ointments are the soft semisolid preparations meant for external application to the skin or mucous membrane. They usually contain a medicament dissolved, suspended or emulsified in the base. Ointments are used for their emollient and protective action to the skin.

Powders
Powders are solid dosage form of medicament meant for internal and external use. The powders meant for internal use are known as oral powders whereas those meant for external use are known as dusting powders: The powders may be simple or compound. When the powders are dispensed in large quantities in a container and the patient is asked to measure a specified quantity as a dose then these powders are known as bulk powders. Examples are dextrose oral powder, talc dusting powder etc.

Solutions
Solutions are liquid preparations meant for internal or external use. They contain one or more than one ingredient usually dissolved in water. They may be sterile when intended for parenteral administration or unsterilized when untended for oral administration.

Spirits
Spirits are solutions of medicament or medicaments in alcohol (90 per cent). Examples are chloroform spirit, lemon spirit, compound orange spirit.

Sprays
Sprays are the liquid preparations of medicaments in aqueous, alcoholic or glycerin containing vehicle and are meant for application to the nose or throat by means of an atomizer or nebuliser.

Suppositories
Suppositories are special shaped solid dosage form of medicament for insertion into body cavities other than mouth. They may be inserted into rectum, vagina or urethra. These products are so formulated that after insertion, they will either melt or dissolve in the cavity fluids to release the medicament. Suppositories vary in shapes, sizes and weights. Generally suppositories from 1 to 2 gm are prepared with either cocoa butter or glycerol gelatin base.

Suspensions
Suspensions are the biphasic liquid dosage form of medicament in which the finely divided solid particles ranging from 0.5 to 5.0 micron are suspended or dispersed in a liquid or semisolid vehicle. Suspensions are mainly used for oral administration, external application or parenteral use.

Syrups
Syrups are sweet, viscous, concentrated aqueous solutions of sucrose or other sugars in water or any other suitable aqueous vehicle. They are used as sweetening and flavoring agents.

Tablets
Tablets are unit solid dosage form of medicament or medicaments with or without suitable diluents. They are prepared by molding or usually by compression. Tablets are generally meant for oral administration but may be used by other routes of administration.

Tinctures
Tinctures are alcoholic liquid preparations containing the active principles of vegetable drugs. They are usually prepared by maceration or percolation, or may be prepared by dissolving the corresponding liquid extract or chemical substances in alcohol or hydro alcoholic solvent.



Fate of drug administration includes the followings:
§ Absorption
§ Distribution
§ Elimination


§ Absorption, which involves disintegration and dissolution.
§ Distribution, which means distributed through blood circulatory system and reaches the desired sites (cells, tissues and organs) and gives pharmacological actions.
§ Elimination, drug elimination refers to the irreversible removal of drug from the body from the body by all routes of elimination. Drug elimination involves metabolism (biotransformation) and excretion.

Metabolism has two phases, in phase-I biotransformation reaction occur first and introduce or expose a functional group on the drug molecule (asynthetic reactions, includes oxidation, reduction and hydrolysis), in phase-II conjugation reaction occurs (synthetic reactions, glucuronide conjugation, peptide conjugation, methylation, acetylation, sulfate conjugation).

Excretion is the removal of the intact drug. Nonvolatile drugs are excreted mainly by renal excretion. Other pathways for drug excretion may include the excretion of drug into bile, sweat, saliva, milk (via lactation) or other body fluids. Volatile drugs, such as gaseous anesthetics or drugs with high volatility are excreted via the lungs into expired air.